This is one of those employment law questions that has gotten a fair amount of attention in the courts and the workplace. Generally, employers have to worry about complying with various laws that ensure a workplace is safe and non-hostile. Claims of this nature have been filed by workers on both sides of such situations under the federal ADA (Americans with Disabilities Act) against employers. Take a look at the following hyperlinks that discuss the issues as construed by federal courts in such cases: "The scent of disability discrimination" (October 12, 2007) at http://www.hrhero.com/hl/101207-ct-scent.shtml and "Perfume Sensitivity and the ADA" (July 9, 2007) at http://employment.lawfirmnewjersey.com/archives/ada-perfume-sensitivity-and-the-ada.html. You should also take a look at your company's policies and procedures manual, employee's handbook, or similar publication to see if it addresses such issues.
Are you in a union? If so, then you should talk to your union rep about whether they are changing the terms and conditions of employment. Otherwise, I would say the answer is yes, the employer can do this. As the prior answer identifies, employers are worried about getting sued by employees who have disabilities, and employers are required go out of their way and take reasonable steps to reasonably accommodate an employee's disability. Where, as here, an employee has multiple chemical sensitivity syndrome or something similar, the law may well REQUIRE the employer to tell you to stop wearing the perfume, and if you refuse a direct order from a supervisor it is considered insubordination. Hope this helps. -Don